From: Nicolas Boichat <drinkcat@xxxxxxxxxxxx>
Subject: mm/failslab.c: by default, do not fail allocations with direct reclaim only
When failslab was originally written, the intention of the
"ignore-gfp-wait" flag default value ("N") was to fail GFP_ATOMIC
allocations. Those were defined as (__GFP_HIGH), and the code would test
for __GFP_WAIT (0x10u).
However, since then, __GFP_WAIT was replaced by __GFP_RECLAIM
(___GFP_DIRECT_RECLAIM|___GFP_KSWAPD_RECLAIM), and GFP_ATOMIC is now
defined as (__GFP_HIGH|__GFP_ATOMIC|__GFP_KSWAPD_RECLAIM).
This means that when the flag is false, almost no allocation ever fails
(as even GFP_ATOMIC allocations contain ___GFP_KSWAPD_RECLAIM).
Restore the original intent of the code, by ignoring calls that directly
reclaim only (__GFP_DIRECT_RECLAIM), and thus, failing GFP_ATOMIC calls
again by default.
Link: http://lkml.kernel.org/r/20190520214514.81360-1-drinkcat@xxxxxxxxxxxx
Fixes: 71baba4b92dc1fa1 ("mm, page_alloc: rename __GFP_WAIT to __GFP_RECLAIM")
Signed-off-by: Nicolas Boichat <drinkcat@xxxxxxxxxxxx>
Reviewed-by: Akinobu Mita <akinobu.mita@xxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/failslab.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/mm/failslab.c~mm-failslab-by-default-do-not-fail-allocations-with-direct-reclaim-only
+++ a/mm/failslab.c
@@ -23,7 +23,8 @@ bool __should_failslab(struct kmem_cache
if (gfpflags & __GFP_NOFAIL)
return false;
- if (failslab.ignore_gfp_reclaim && (gfpflags & __GFP_RECLAIM))
+ if (failslab.ignore_gfp_reclaim &&
+ (gfpflags & __GFP_DIRECT_RECLAIM))
return false;
if (failslab.cache_filter && !(s->flags & SLAB_FAILSLAB))
_
